I am sure this would work well in many dry areas of southern Europe and arid parts of the US, Africa and Australia.

The test site in Germany near the Bodensee was interesting because Germany too suffered a drought in 2018. Not talked about in the UK, but the Rhine was so dry, ot could be walked across around Dusseldorf.The reference unshaded potato crop would have been well down compared to a non drought year. Also the earthing up of the potatoes would cause increased water loss from the surrounding soil due to its increased surface area. Ie not flat ground. A comparison with grain or maize would also be a useful comparison too.Philip R